Older & cheaper heart disease test just as effective as newer, expensive ones

An older and cheaper diagnostic test for heart disease is as effective as newer, costlier cardiac tests according to a new study from Institute of Evaluative Clinical Sciences (ICES) led by Sunnybrook cardiologists.

Physicians use diagnostic imaging and testing to determine the cause of coronary artery disease — where the arteries that supply blood to the heart become hardened or narrowed. One of those tests is a decades-old exercise stress test. Also known as a graded exercise test (GXT), it evaluates the heart’s response to physical activity as the participant runs on a treadmill or rides a stationary bike.

The study that was recently published in the Journal of the American Heart Association compared the GXT with three other non-invasive tests used in Ontario for coronary artery disease, the second leading cause of death in Canada.

• Stress echocardiography (Stress echo), which uses ultrasonic waves (ultrasound) to record moving images of the heart.
• Coronary computed tomography angiography (CCTA) assesses any narrowing or blockages in the arteries that supply blood to the heart muscle by injecting an intravenous dye and using a CT scanner.
• Myocardial perfusion imaging (MPI), also called a nuclear stress test, uses radioactive material called tracers to show how well blood flows through the heart.

“There is a trend to do tests other than GXT as first-line [diagnostic] tests with the thought being that they provide more information about heart structure and/or function,” says Dr. Idan Roifman, an adjunct scientist at ICES, staff cardiologist at Schulich Heart Centre and lead author of the study. “We therefore expected clinical outcomes to be better for those patients.”

But that wasn’t the case.

The researchers examined records for 15,467 Ontario adults who underwent a non-invasive diagnostic test in 2012, followed by angiography — a minimally-invasive procedure for diagnosing coronary artery disease. It involves inserting a catheter into an artery (usually in the groin) and threading it up to the heart. Contrast dye is then injected to light up the arteries like a Christmas tree to identify the blockages.

“We found that none of the other [non-invasive diagnostic] tests performed better at identifying patients with significant coronary disease than the oldest and least expensive one, the GXT,” says Roifman. More importantly, he adds, “patients who first underwent the other tests — stress echo, CCTA and MPI — didn’t have improved clinical outcomes down the road.”

The researchers emphasize that approximately 20 per cent of patients are ineligible to undergo a GXT.

And while the researchers do see a potential for cost savings, the study did not draw any conclusions. Roifman says the cost analysis is the next step for his team.